A known power seat apparatus for a vehicle includes a speed reduction device that reduces a rotational speed of an output shaft of a drive source such as an electric motor and then transmits the resulting rotational speed (i.e., the rotation) to a drive shaft driving a movable portion of the power seat. DE10327103A1 (hereinafter referred to as Reference 1) discloses such speed reduction device. According to Reference 1, an electric motor (motor) includes two attachment portions where through-holes are formed respectively. Two screws are inserted into the respective through-holes so as to be meshed with respective internal threads provided at a gear reduction box. As a result, the motor is securely fixed to the gear reduction box.
In addition, according to JPH10-147164A (hereinafter referred to as Reference 2), an output shaft of an electric motor (motor) and a reducer portion provided within a casing are connected to each other by means of a cable to thereby transmit a driving force of the motor to the reducer portion. The motor is securely fixed to a slide bracket via two screws and the casing is also fixed to the slide bracket via two screws.
According to Reference 1, the two screws are necessary to fix the motor to the gear reduction gearbox. In addition, the internal threads formed at the gear reduction gearbox and tightening of the two screws may lead to an increase of a manufacturing cost. Further, according to Reference 2, the two screws are required and tightened to fix the motor to the slide bracket, which may also lead to an increase of a manufacturing cost.
A need thus exists for a speed reduction device for a power seat which is not susceptible to the drawback mentioned above.